Parallel kinematic mechanisms with decoupled rotational motions

Abstract

A parallel kinematic mechanism apparatus includes a frame, a handle and an input joint that connects having at least two independent and functionally parallel paths for transmission of motion coupling the handle to the frame. A first path includes a first intermediate body connected to the frame by a first connector and to the handle by a third connector while the second path that is independent from the first path includes a second intermediate body that is connected to the frame by a second connector and to the handle by a fourth connector. The first connector and the fourth connector both allow rotation in a first rotational direction and restrict rotation in a second rotational direction and the second and third connectors allow rotation in the second rotational direction and restrict rotation in the first rotational direction.

What is claimed is: 
     
       1. A parallel kinematic (PK) mechanism having at least two rotational degrees of freedom between a handle and a frame, the PK mechanism comprising:
 the frame; 
 the handle; 
 an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path; 
 a first intermediate body in the first path that is connected to the frame by a first connector and to the handle by a third connector; 
 a second intermediate body in the second path that is connected to the frame by a second connector and to the handle by a fourth connector; 
 wherein the first connector and the fourth connector both allow rotation in a first direction and restrict rotation in a second direction; 
 further wherein the second and third connectors allow rotation in the second direction and restrict rotation in the first direction. 
 
     
     
       2. The parallel kinematic mechanism of  claim 1 , wherein an angle between an axis of rotation of the first direction and an axis of rotation of the second direction is between 30 and 150 degrees. 
     
     
       3. The parallel kinematic mechanism of  claim 1 , wherein an axis of rotation of the first direction is orthogonal to an axis of rotation of the second direction. 
     
     
       4. The parallel kinematic mechanism of  claim 1  wherein an axis of rotation of the first direction and an axis of rotation of the second direction intersect in a virtual center of rotation, further wherein the virtual center of rotation is located in a vacant space devoid of any other components of the parallel kinematic mechanism or attached to the parallel kinematic mechanism. 
     
     
       5. The parallel kinematic mechanism of  claim 4 , wherein the virtual center of rotation coincides with a center of a user's articulating joint when the user interfaces with the handle. 
     
     
       6. The parallel kinematic mechanism of  claim 4 , wherein the virtual center of rotation coincides with a center of a user's wrist joint when the user is holding the handle. 
     
     
       7. The parallel kinematic mechanism of  claim 1  configured as a portion of a minimally invasive tool further comprising a tool shaft having a proximal end and a distal end, wherein the proximal end of the tool shaft is connected to the frame. 
     
     
       8. The parallel kinematic mechanism of  claim 7 , wherein the minimally invasive tool further comprises an output joint with at least two rotational degrees of freedom between an end effector and the distal end of the tool shaft wherein the output joint is coupled to the input joint via a transmission system to correlate and transmit the at least rotations of the input joint to the at least two rotational degrees of freedom of the output joint. 
     
     
       9. The parallel kinematic mechanism of  claim 7  wherein the minimally invasive tool further comprises an end effector connected to the tool shaft via an output joint having at least two rotational degrees of freedom between the end effector and the distal end of the tool shaft, wherein the output joint is coupled to the input joint via a transmission system to correlate and transmit rotations of the handle with respect to the frame to corresponding rotations of the end effector with respect to the tool shaft. 
     
     
       10. The parallel kinematic mechanism of  claim 1  further comprising an output joint wherein the output joint is coupled to the input joint via a purely mechanical transmission system configured to correlate and transmit rotations of the first and second intermediate bodies to the output joint. 
     
     
       11. The parallel kinematic mechanism of  claim 1  further comprising an output joint wherein the output joint is coupled to the input joint via an electromechanical transmission system configured to correlate and transmit rotations of the first and second intermediate bodies to the output joint. 
     
     
       12. The parallel kinematic mechanism of  claim 1  further comprising an output joint wherein the output joint is coupled to the input joint via a fluidic transmission configured to correlate and transmit rotations of the first and second intermediate bodies to the output joint. 
     
     
       13. The parallel kinematic mechanism of  claim 1 , wherein the frame is configured to interface with the forearm of a user. 
     
     
       14. The parallel kinematic mechanism of  claim 1 , wherein the first and second intermediate bodies comprises pulleys. 
     
     
       15. The parallel kinematic mechanism of  claim 1 , wherein the first connector is a first pivot joint, the second connector is a second pivot joint, the third connector is a first flexure transmission strip and the fourth connector is a second flexure transmission strip. 
     
     
       16. The parallel kinematic mechanism of  claim 1 , wherein the input joint comprises a third independent path for transmission of motion coupling the handle to the frame, wherein the third independent path operates in parallel with the first and second paths;
 a third intermediate body in the third independent path that is connected to the frame by a fifth connector and to the handle by a sixth connector; 
 wherein the fifth connector allows rotation in the first direction and restricts rotation in the second direction and the sixth connector allows rotation in the second direction and restricts rotation in the first direction. 
 
     
     
       17. The parallel kinematic mechanism of  claim 1 , wherein the first path and the second path allow translation along a third direction orthogonal to first and second directions. 
     
     
       18. The parallel kinematic mechanism of  claim 1 , wherein the first path or the second path or both the first path and the second path constrain(s) rotation about a third direction orthogonal to first and second directions. 
     
     
       19. A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame, the PK mechanism comprising:
 the frame; 
 the handle; 
 an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path; 
 a first intermediate body comprising a first pulley in the first path that is connected to the frame by a first connector comprising a first pulley pin and to the handle by a third connector comprising a first transmission strip; 
 a second intermediate body comprising a second pulley in the second path that is connected to the frame by a second connector comprising a second pulley pin and wherein the second intermediate body is connected to the handle by a fourth connector comprising a second transmission strip; 
 wherein the first pulley pin allows rotation in a pitch direction and restricts rotation in a yaw direction, and the second transmission strip is compliant in bending in the pitch direction and has a high stiffness in bending in the yaw direction; 
 further wherein the second pulley pin allows rotation in the yaw direction and restricts rotation in the pitch direction and the first transmission strip is compliant in the yaw direction and has high stiffness in bending in the pitch direction. 
 
     
     
       20. The parallel kinematic mechanism of  claim 19 , wherein the first and second transmission strips comprise a plurality of rigid segments serially connected by hinged connections. 
     
     
       21. The parallel kinematic mechanism of  claim 19 , wherein the first and second transmission strips comprise a plurality of rigid segments and a plurality of hinges, wherein each rigid segment is hinged to an adjacent rigid segment by a hinge from the plurality of hinges, and wherein each hinge has an axis of rotation that is parallel to an axis of rotation of each hinge in the plurality of hinges, and wherein the hinges can be traditional hinges or living hinges or a combination thereof. 
     
     
       22. The parallel kinematic mechanism of  claim 19 , wherein a first end of the first transmission strip is attached to the handle and an opposite end of the first transmission strip is attached to the first pulley; further wherein the first end of the second transmission strip is attached to the handle and an opposite end of the second transmission strip is attached to the second pulley. 
     
     
       23. The parallel kinematic mechanism of  claim 19 , wherein the first and second transmission strips allow translation along a third direction that is orthogonal to the first direction and the second direction. 
     
     
       24. The parallel kinematic mechanism of  claim 19 , wherein the first path, or the second path, or the first and second paths constrain rotation along a third direction that is orthogonal to the first direction and the second direction. 
     
     
       25. The parallel kinematic mechanism of  claim 19 , wherein the first and second transmission strips comprise a plurality of rigid segments and a plurality of hinges, wherein each rigid segment is hinged to an adjacent rigid segment by a hinge from the plurality of hinges, and wherein at least some of the hinges comprise living hinges. 
     
     
       26. A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame comprising:
 a frame; 
 a handle comprising a plate; 
 an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path; 
 a first intermediate body comprising a first plate in the first path that is connected to the frame by a first connector comprising a first plurality of transmission strips and to the handle by a third connector comprising a third plurality of transmission strips; 
 a second intermediate body comprising a second plate in the second path that is connected to the frame by a second connector comprising a second plurality of transmission strips and to the handle by a fourth connector comprising a fourth plurality of transmission strips; 
 wherein the first connector and the fourth connector both allow rotation in a pitch direction and restrict rotation in a yaw direction; 
 further wherein the second and third connectors allow rotation in the yaw direction and restrict rotation in the pitch direction. 
 
     
     
       27. The parallel kinematic mechanism of  claim 26 , wherein the first plurality of transmission strips and the fourth plurality of transmission strips are compliant in bending in the pitch direction and have a high stiffness in bending about the yaw direction and wherein the second plurality of transmission strips and the third plurality of transmission strips are compliant in bending in the yaw direction and have a high stiffness in bending about the pitch direction. 
     
     
       28. The parallel kinematic mechanism of  claim 26 , wherein the each transmission strip in the first plurality of transmission strips is rigidly attached at a first end to the first intermediate body and is rigidly attached at a second end opposite from the first end to the frame; and wherein each transmission strip in the third plurality of transmission strips is rigidly attached at a first end to the first intermediate body and is rigidly attached at a second send opposite from the first end to the handle. 
     
     
       29. A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame comprising:
 a frame; 
 a handle; 
 an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path; 
 a first intermediate body comprising a pitch mount in the first path that is connected to the frame by a first connector comprising a pivot joint and to the handle by a third connector; 
 a second intermediate body comprising a yaw mount in the second path that is connected to the frame by a second connector comprising a pivot joint and to the handle by a fourth connector; 
 wherein the first connector and the fourth connector both allow rotation in a pitch direction and restrict rotation in a yaw direction; 
 further wherein the second and third connectors allow rotation in the yaw direction and restrict rotation in the pitch direction. 
 
     
     
       30. The parallel kinematic mechanism of  claim 29 , wherein the first intermediate body comprises a pulley rigidly coupled to the pitch mount and wherein the second intermediate body comprises a yaw pulley rigidly coupled to the yaw mount. 
     
     
       31. The parallel kinematic mechanism of  claim 29 , further wherein the first path, or the second path, or the first and the second paths constrain the handle or the member rigidly extending from the handle from rotating about a roll axis that is orthogonal to both the pitch and yaw axes. 
     
     
       32. The parallel kinematic mechanism of  claim 29 , further wherein the first path and the second path allow the handle or the member rigidly extending from the handle to translate along a roll axis that is orthogonal to both the pitch and yaw axes.